Keying system



Feb. 27, 1934. FARRINGTON 1,949,248

' KEYING SYSTEM Filed June 10, 1930 FIG. I

FIG. 2

INVENTOR JOHN E FARRINGTON ATTORNEY Patented Feb. 27, 1934 UNITED STAE KEYIN G SYSTEM John Fish Farrington, Flushing, N. Y., asslgnor to International Communications Laboratories, Incorporated, New York, N. Y., a corporation of New York Application June 10, 1930. Serial No. 460,278

13 Claims.

- My invention relates to radio transmission systems, and particularly to such systems having means incorporated therein for stabilizing the transmission frequency.

' It has for an object the production of a new and useful system of keying an oscillation generator, as well as means for the maintenance of steady temperature and electrode spacing conditions within a generator in a transmission sysitem. It has for a further object the maintenance of constant temperature conditions within a generator device during the physical changes that occur between signalling and spacing per-iods, and the production of a new and improved Si steam for maintaining the load condition cons an In the generation of radio signals at ultra-high frequencies for use in signal channels, it has been found that changes in temperature of the genlerator elements such as the electrodes, caused by the change in load level and energy dissipation between signalling and spacing periods, may cause changes in the physical dimensions of said elements and correspondingly in the interelectrode capacity; and thus produce undesirable changes in the generated frequency. At frequencies such as 3,000 kilocycles and above, the change in frequency with change in temperature of the electrodes due to this cause is sufficient to modify a beat note frequency produced ina heterodyne oscillation receiver so greatly as to make the reading of the code difiicult.

My invention provides means for keeping more nearly constant the energy load upon the gener- 'ator, so that the energy dissipated in it is kept substantially constant and undue changes in the electrode temperature and physical dimensions are avoided, and so that troublesome variations in frequency from such factors are prevented. By this means I am enabled to improve the performance of a transmitting triode and simplify the reception of signals therefrom.

Additional objects and advantages of my invention, as well as the apparatus and method employed in the practice thereof, will be apparent from the following description, when read in connection with the accompanying drawing; wherein {Figure 1 is an embodiment of a simple form of the system of my invention, and

Fig. 2 is an alternative embodiment. Referring to Fig. 1, the system may comprise an oscillation generator such as a triode 1 havinga resonant plate circuit containing an inductance 2 and capacitance 3, coupled to an aerial circuit consisting of an antenna 4, coupling inductance 5 and ground 6. A current supply such as a dynamo 7 for the plate circuit power, a by-pass condenser 8, and a radio frequency choke 9 are likewise provided, as well as a similar current supply such as a dynamo 11 for the filament heating circuit. A grid inductance 12, connected between the grid and filament is also included. In the generator system as above described is further included a key 14 or an equivalent relay, 05 connected between the inductance 12 and the filament circuit as shown. The contacts of the key or relay 14 are shunted by an impedance 15. The inductance 12 is designed or adjusted to a value suitable to allow the production of oscillations in the generator system at the desired frequency when the key 14 is closed. The impedance 15, which may desirably be an inductance,

is adjusted to a value such as to stop oscillation of the system when it is thrown into the grid circuit by the opening of the key 14.

This embodiment of my invention thus functions in the usual way for the generation and radiation of oscillations when the key 14 is closed for a marking period. When the key 14 is opened for a spacing period, the triode system ceases to oscillate, but the plate current may be kept substantially constant at the oscillating value by appropriate adjustment of circuit factors. This system thus keeps the plate current and the total energy out-put substantially constant between signalling and spacing periods; and accordingly, negligible temperature and dimensional changes occur in the electrodes, and a negligible frequency variation appears from such effects.

Alternatively, the embodiment shown in Fig. 2 may be utilized. Broadly, this system provides means for the supply of a low frequency oscillation to the generator system during spacing periods and the absorption of low frequency energy output therefrom during the same time. In the particular embodiment here disclosed, the grid potential swing produced by the low frequency non-signalling oscillations may be made substantially the same as the grid potential swing produced by the high frequency energy generated during signalling oscillations, and the output energy absorbed at the low frequency may be adjusted to approximately the value of energy absorbed in the aerial circuit during high frequency signalling periods.

This system may comprise a triode l as in the first embodiment, in the plate circuit of which is connected an output system consisting of an inductance 2 and a. capacitance 3 associated with an aerial circuit having an antenna 4, an inductance 5 and a ground connection 6. A plate circuit current source such as a dynamo 7, a by-pass condenser 8, a radio frequency choke 9, a filament 5 current source such as a dynamo 11, and a grid inductance 12 are provided as before.

A double contact key or relay 16 is provided, one pair of contacts being connected between the filament of the triode and the grid inductance 12. These contacts are shunted by an impedance as in the previously described embodiment. A by-pass condenser 17 is connected. between the impedance 15 and the filament to pass the radio frequency oscillations in the grid 15 circuit.

A source of low frequency oscillations 18 is also provided. This may be a commercial-power-frequency dynamo if desired, or may be any convenient generator of a frequency well removed 20 from the generation frequency of the triode. It is connected to a transformer 19 whose primary circuit is closed through the second pair of contacts of the key or relay 16.

The secondary coil of the transformer 19 is ;connected in the grid circuit, shunted by the condenser 17, and connected to the key contacts and the impedance 15 as shown.

A second transformer 21 is also provided and the primary coil thereof is connected between soiithe plate circuit generator 8 and the anode of the triode l. The secondary of the transformer 21 is connected to an adjustable resistance 22.

In the operation of this embodiment of the system of my invention, the key 16 may be closed 35, ,to shunt the impedance 15, whereupon oscillations are produced and radiated in the usual way. When the key 16 is opened, the impedance 15 is inserted in the circuit and stops the genera.- tion of oscillations by the triode. Simultaneous- 40. 'ly, the back contacts of the key 16 are closed and energy from the generator 18 is impressed through the transformer 19 upon the grid circuit through the impedance 15 and the inductance 12. This frequency being low is not radiated by the antenna 4 but appears in amplified form in the plate circuit. The transformer 21 passes a substantial portion of the low frequency energy to the resistance 22 where it is absorbed and dissipated as heat, while the by-pass condenser 8 in so. conjunction with inductance 9 keeps the high frequency from passing through the circuit of transformer 21.

In this embodiment, signalling oscillations are generated during the period that the key 16 is closed. When the key 16 is open, however, the

system ceases to generate oscillations at the radiation frequency, but the grid is kept active by the application of oscillations at a very different frequency. The amplitude of these oscillations 6; is desirably adjusted to correspond closely to the amplitude of those impressed at radio frequency. During the signalling period a substantial amount of oscillatory energy is transferred from the plate circuit through the inductance 2 6:1 to the aerial circuit and radiated therefrom. During the spacing period no low frequency energy is radiated from the antenna 4 but a substantial amount is passed through the transformer 21 and absorbed in the resistance 22.

'1 By this means, the triode 1 is kept energized at a constant level during both signalling and spacing' periods, normal radio frequency oscillations being passed therethrough during signalling periods and non-radiatable low frequency oscilla- 75. tions being passed through at substantially thev same energy level during non-oscillating spacing periods.

By this system the triodes of a signal generator are kept continuously energized at a steady energy level and a constant energy throughout maintained during both the signalling and, spacing periods. Accordingly, the energy dissipated in the triode is kept constant and thereby the temperature and physical dimensions, for the stabili-- zation of the radiated signal frequency.

While I have shown but two embodiments of the principle of my invention, other modifications are possible without essential departure; and the appended claims are to be construed as broadly as is consonant with the real spirit and scope of the invention.

I claim as my invention:

1. A- signalling system comprising, a. signal channel, a source of oscillatory energy connected thereto, a signal controlling means connected to said source, and means associated with the aforesaid means for maintaining the energy outputlot. said source at a substantially constant. level dur-= ing marking and spacing periods, comprising auxiliary source of non-radiatable oscillations 1(1) sociated with said source and an absorbingmeann for said auxiliary oscillations.

2. A radio signalling system, comprising a vac! uum tube and oscillation producing circuits con.- nected thereto, a key in the control circuitthereof, and means associated with said. key: compris ing an impedance for stopping oscillations when. said key is open while maintaining the energy,- level therein approximately constant.

3. A radio signalling system,rcomprising; avac- 1w uum tube and oscillation producing circuits connected thereto, a key in the control circuit thereof, and means associated with said key-comprising an impedance and a source of. 0861118? tory energy at a widely different frequency, fox-115, stopping oscillations at a radiatable frequency; when said key is open while maintaining; the, energy input level at said grid. approximately. constant.

i. A radio signalling system, comprisingatrioda'mo, and oscillation producing circuits connectedthereto, a key in the grid circuit thereof, and, means associated with said key comprising an impedance and a source of oscillatory energy at s. widely different frequency for stopping tions when said key is open while maintaining tho energy input level at said grid approximately-constant, and means in the output circuit thereot for absorbing energy at said different frequency.

5. In a radio signalling system, a generator 1m oscillation circuits associated therewith, a key connected. thereto for controlling. oscillation; thereof, means operated by said key for applying thereto a widely different frequency during specing periods, means associated with said circuits 135, for the radiation of energy during signalling; periods, and means also associated with said cir cuits for absorbing energy at said widely different frequency during spacing periods.

6. In a radio signalling system, a triode,v calls 140, lation circuits associated therewith, a keg connected thereto for controlling oscillationsithere' of, means operated by said key for applying; tether grid of said triode a widely different frequency during spacing periods, means associated with said circuits for the radiation of energy during signalling periods, and means also associated with said circuits for absorbing energy: at. said; widely diiferent frequency during. spacing-periods,. the energy input to the grid during W150,

periods being adjusted to approximately the same energy level as the input to the grid during signalling periods, and the energy absorbed by the absorbing means being adjusted to a value approximately equal to the value of the energy radiated during signalling periods, whereby the energy level through the tube circuits is maintained substantially constant during signalling and spacing periods.

7. In a radio signalling system, a triode, oscillation producing circuits associated therewith, means for the control thereof comprising a key and an oscillation choke connected in said circuits, means for the radiating of said oscillations comprising an antenna system, auxiliary means for impressing a low non-radiatable frequency to said triode during spacing periods comprising a source of low frequency alternating current, a transformer and by-pass condenser connected in said oscillation producing circuits, an auxiliary key for the control of said low frequency alternating current, and an absorbing system comprising a transformer and a resistance connected thereto, associated with the output circuit of said triode.

8. The method of operating a signal transmis sion system which comprises producing conveyable self-oscillations by a generator therein during marking periods, and converting said generator into an amplifier and producing therein nonconveyable auxiliary oscillations during spacing periods.

9. The method of operating a signal channel which comprises producing conveyable oscillations therein during signal marking periods, and transmitting said oscillations to remote point, and converting said generator into an amplifier and producing non-conveyable oscillations therein during spacing periods, and absorbing them at a point adjacent the amplifier.

10. The method of operating a signal generator having input and output circuits which comprises causing it to generate oscillations during signalling periods and maintaining the energy level in said input and output circuits at substantially the same value during both signaling and spacing periods.

11. The method of operating a signal generator which comprises causing it to generate oscillations during signalling periods, converting said generator into an amplifier at the end of each signalling period, and impressing thereon energy at a widely different frequency during spacing periods only.

12. In a radio transmitter, the combination of an electron tube oscillation generator having coupled input and output circuits, a power source for said output circuit, signalling means for providing marking and spacing signals, means for causing the energy dissipation in the tube to be the same during spacing as during marking periods, and means controlled by the signalling means for causing the tube to cease generation of oscillations during spacing periods and to produce oscillations during marking periods.

13. In a radio transmitter, the combination of an electron tube oscillation generator having coupled input and output circuits, a power source for said output circuit, signalling means for providing marking and spacing signals, means for causing the energy dissipation in the tube to be the same during spacing as during marking periods, and a choke coil so controlled by the signalling means that during marking intervals it is excluded from the input circuit allowing the tube to generate oscillations and during spacing intervals is included in the input circuit thereby causing the tube to cease generation of oscillations.

JOHN F. FARRINGTON. 

